Alright I just recently got my Stag 16" M4.

Bought the upper complete and built the rest myself. Fired 90 WWB 55gr FMJ through it perfectly. Cleaned and lubed afterwards. I go down to the indoor range that just recently opened where I have to buy their stuff.

So they give me 60 rounds of Winchester USA 55gr FMJ 5.56mm. The Q3131.

First couple rounds fire fine, and then after that, after every round, I have to pull the charging handle. It just refuses to cycle another round into the chamber. Jammed ALOT too. Took it to the gunsmith there, he stripped it, oiled it, said it looked perfectly fine.

He tried one last thing, where he put a little oil on the 4 rounds left and they shot fine...

My gun is chambered for 5.56mm. So I go back to the desk and ask for different ammo. Luckily, he found some Federal American Eagle .223 55gt FMJ. Shot flawlessly.

YET, the next guy after me came in with a RRA Carbine, using that Q3131, and it shot fine, yet I bought 3 boxes and had nothing but trouble.

Why? My gun HATES that stuff.

Here is a pic. To recap, Q3131 shot the worst I have ever seen. Switched over to the American Eagle making no changes to the rifle, and shot 40 rounds flawlessly.

dubisteinspundloch.com/DSCF4898.JPG

Quoted: Quoted: He tried one last thing, where he put a little oil on the 4 rounds left and they shot fine... Sounds like the chamber is on the new/rough side, and may even be complicated by lack of correct cleaning methods. May just need to break the upper in, and when you’re done with the copper solvent after cleaning the bore, make sure to completely flush it out of the chamber/bore.  Solvents like Hoppes copper solvent get sticky when hot, and can really collect fouling fast.

Haven't used copper solvent yet.  Just Hoppes #9.  Fired about 190 rounds through it

Quoted: AR rifles are lubed and cleaned with CLP. The bores are cleaned with a copper solvent, but the copper solvent is flush out of the rifle after being used. If you are not familiar with CLP, go buy a big spray can of BreakfreeCLP.  Wal-mart sells the big 16 oz cans for under $10. Note: the difference between standard gun oil and CLP is that CLP has an active cleaning agent that will dissolve gunpowder fouling as it tries to build up in the rifle. As for the rifle being cleaned, it should have broken down and cleaned before you every fired the rifle the first time out. www.ar15.com/content/guides/maintenance/ P.S. it’s early, so if this posts seems off key, it’s just because I haven’t knocked the cobwebs out of my head yet, and trying to get you the information before night crewing it tonight.

I only ran a dry patch through before I shot the rifle.  Just to knock anything out.

As I said, shot fine the first time I took it out.

I use CLP.  Gonna get some copper solvent later on for the bore

Quoted: Bad idea shooting the rifle on it’s madden vogue dirty, and waiting to clean the bore now since the barrels are coated with assembly grease to prevent rusting.  Chances are you baked the grease into the chamber/bore, and now have some chamber/bore scrubbing to get both clean. Trust me, for the first 500 rounds; there is no such thing as over lubing, or over cleaning. Note: in regards to cleaning, these first few hundred rounds are when the rifling is unified (read you want the bore as clean as possible, the chamber broken in, and the barrel tension relieved threw live fire.  Leaving the backed grease or copper fouling just means that it will take longer for the barrel to unify it's rifling, which means longer until the barrel settles in (shoots it's best).

What do you mean waiting?  After I'm done shooting, the first thing I do is clean the bore and everything else.

"What do you mean waiting?  After I'm done shooting, the first thing I do is clean the bore and everything else."
M4A1 -- dano seems to be trying to help you out.  New rifles require a thorough cleaning and lubrication BEFORE firing for the first time.  That gets all the factory grease, cosmoline, whatever they use to keep rust off during storage & shipping, off your rifle.  Clean first time round means less powder fowling = more reliability.  You may or may not have done this.  Doesn't matter now, just clean the heck out of it and lube it before you shoot it again.

If it functions properly with a little lube on the ammo, then i think you'll be fine after you get it cleaned up.  Keep in mind that it will take a little while to break all the parts in.  Shooting it smooths out the little micro surface irregularities that come from machining processes.

Use Hoppe's if you want.  I use it about once a year, at the end of the shooting season.  Rest of the time it's CLP for my personal firearms and for my duty weapons.

Next trip to the range, try lubing it up between magazines.

Not meant to be a flame.  I had the very same problem breaking in my first Ar-15, way back in 1982.  Damn, I wish I still had that rifle.

Quoted: "What do you mean waiting?  After I'm done shooting, the first thing I do is clean the bore and everything else." M4A1 -- dano seems to be trying to help you out.  New rifles require a thorough cleaning and lubrication BEFORE firing for the first time.  That gets all the factory grease, cosmoline, whatever they use to keep rust off during storage & shipping, off your rifle.  Clean first time round means less powder fowling = more reliability.  You may or may not have done this.  Doesn't matter now, just clean the heck out of it and lube it before you shoot it again. If it functions properly with a little lube on the ammo, then i think you'll be fine after you get it cleaned up.  Keep in mind that it will take a little while to break all the parts in.  Shooting it smooths out the little micro surface irregularities that come from machining processes. Use Hoppe's if you want.  I use it about once a year, at the end of the shooting season.  Rest of the time it's CLP for my personal firearms and for my duty weapons. Next trip to the range, try lubing it up between magazines. Not meant to be a flame.  I had the very same problem breaking in my first Ar-15, way back in 1982.  Damn, I wish I still had that rifle.

You use CLP to clean the bore?  Better than Hoppes?  I know it'd probably be way cleaner without shit dripping everywhere.

But I'll let you know what happens next time I go to the range.  I'm just gonna shoot the American Eagle stuff.  Rifle has already been cleaned and lubed as normal.  I'm gonna bring some CLP with me though.

Check your carrier key.  It might be loose.  Check Tweak's thread on securing the carrier key.  You might also want to check the gas tube.  It may be misaligned with the bolt carrier.

Quoted: Check your carrier key.  It might be loose.  Check Tweak's thread on securing the carrier key.  You might also want to check the gas tube.  It may be misaligned with the bolt carrier.

Key is fine.  Even the gunsmith said it was ok.

I doubt it's the gas tube because that other ammo worked fine.